  <!DOCTYPE html>
  <html lang="en">
  <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>事件绑定</title>
  </head>
  <body>
    <button id="btn">点击绑定事件</button>

    <script>
      var btn = document.getElementById('btn');
      btn.addEventListener("click", hello1);
      btn.addEventListener("click", hello2);

      function hello1() {
        alert(hello1);
      };

      function hello2() {
        alert(hello2);
      };
    </script>
  </body>
  </html>